The subject matter herein relates generally to electrical switching devices that are configured to control the flow of an electrical current therethrough.
Electrical switching devices (e.g., contactors, relays) exist today for connecting or disconnecting a power supply to an electrical device or system. For example, an electrical switching device may be used in an electrical meter that monitors power usage by a home or building. Conventional electrical devices include a housing that receives a plurality of output and input terminals and a mechanism for electrically connecting the output and input terminals. Typically, one of the terminals includes a spring arm that is moveable between an open position and a closed position to electrically connect the output and input terminals. In some switching devices, a solenoid actuator is operatively coupled to the spring arm to move the spring arm between the open and closed positions. When the solenoid actuator is triggered or activated, the solenoid actuator generates a predetermined magnetic field that is configured to move the spring arm to establish an electrical connection. The solenoid actuator may also be activated to generate an opposite magnetic field to move the spring arm to disconnect the output and input terminals.
However, a switching device that uses a solenoid actuator as described above is not without disadvantages. For example, the solenoid actuators include a pivot member that actuates multiple spring arms simultaneously. The force required to actuate the spring arms is relatively high and additive because the pivot member is moving multiple spring arms. The solenoid actuator is designed to achieve such force, and the drive coil is sized appropriately to actuate the pivot. Having the drive coil sized larger to overcome the larger force of actuating multiple spring arms requires a larger drive coil, and thus more copper windings for the drive coil, which increases the cost of the drive coil.
Furthermore, switching devices are typically designed with the spring arm being positioned between, and parallel to, stationary blades that form the circuit assemblies of the switching devices. The current tends to travel in a first direction along one stationary blade, in a second direction along the spring arm, and then back in the first direction along the other stationary blade. The current traveling in opposite directions down one of the stationary blades creates a magnetic field and force on the spring arm in a direction that tends to close the spring arm. However, the current traveling down the other stationary blade creates a magnetic field and force on the spring arm in the opposite direction that tends to open the spring arm. These force counteract one another, and the opening force tends to negate the advantage received from the closing force. Additionally, the layering of the stationary blades and spring arm tends to create a long current path through the switching device, which increases the heat generated by the terminals, in some situations to unacceptable levels.
Accordingly, there is a need for electrical switching devices that simplify and reduce the cost of the switching device. There is a need for a switching device that meets temperature rise and short circuit requirements of the industry.